The Experts below are selected from a list of 138 Experts worldwide ranked by ideXlab platform
John C. Defries - One of the best experts on this subject based on the ideXlab platform.
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DeFries–Fulker and Pearson–Aitken Model-fitting Analyses of Reading Performance Data from Selected and Unselected Twin Pairs
Behavior Genetics, 2008Co-Authors: Jesse L. Hawke, Michael C. Stallings, Sally J. Wadsworth, John C. DefriesAbstract:Although a comparison of concordance rates for deviant scores in identical and Fraternal Twin pairs can provide prima facie evidence for a genetic etiology, information is not fully utilized when continuous measures are analyzed in a dichotomous manner. Thus, DeFries and Fulker (Behav Genet 15:467–473, 1985 ; Acta Genet Med Gemellol, 37:205–216, 1988) developed a regression-based methodology (DF analysis) to assess genetic etiology in both selected and unselected Twin samples. While the DF analysis is a very versatile and relatively powerful statistical approach, it is not easily extended to the multivariate case. In contrast, structural equation models may be readily extended to analyze multivariate data sets (Neale and Cardon, Methodology for genetic studies of Twins and families, 1992 ). However, such methodologies may yield biased estimates of additive genetic, shared environmental, and non-shared environmental influences when multivariate models are fitted to selected Twin data. Therefore, the Pearson–Aitken (PA) selection formula (Aitken, Proc Edinburgh Math Soc B, 4:106–110, 1934 ) was used to analyze reading performance data from Twins with reading difficulties (selected sample) and a population of normally-achieving Twin pairs (control sample). As a comparison, DF models were also fitted to these same data sets. In general, resulting estimates of additive genetic, shared environmental, and non-shared environmental influences were similar when the DF and PA models were fitted to the data. However, the PA selection formula may be more readily generalized to the multivariate case.
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Comorbidity of Mathematics and Reading Deficits: Evidence for a Genetic Etiology
Behavior Genetics, 1997Co-Authors: Valerie S. Knopik, Maricela Alarcón, John C. DefriesAbstract:In order to assess the genetic etiology of the comorbidity of reading and mathematics difficulties, data were ascertained from two samples: (1) 102 identical and 77 same-sex Fraternal Twin pairs in which at least one member of each pair is reading disabled and (2) 42 identical and 23 same-sex Fraternal Twin pairs in which at least one member is math disabled. Composite reading and mathematics performance data from each sample were fitted to the basic multiple regression model for the analysis of selected Twin data and its bivariate extension. Resulting estimates of bivariate heritability and the genetic correlation between the reading and the mathematics performance measures suggest that the comorbidity between mathematics and reading difficulties is due in part to genetic influences.
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Gender differences in cognitive abilities of opposite-sex and same-sex Twin pairs with reading disabilty.
Annals of Dyslexia, 1996Co-Authors: Valerie S. Knopik, John C. Defries, Maricela AlarcónAbstract:In order to compare the pattern of gender differences for cognitive measures in opposite-sex Twin pairs to that in independent samples of Twins from same-sex pairs, psychometric test data were obtained from four research-identified samples of children: (1) 96 pairs of opposite-sex Fraternal Twins in which at least one member of each pair is reading disabled; (2) 62 pairs of opposite-sex Fraternal Twins with no history of reading problems; (3) 167 males and 155 females from same-sex identical and same-sex Fraternal Twin pairs in which at least one member of each pair is reading disabled; and (4) a comparison sample of 126 males and 132 females from same-sex Twin pairs with no history of reading problems. Results of multivariate analyses indicate that gender differences for cognitive measures are similar in Twin pairs with and without reading disabilities. Moreover, a highly similar pattern of gender differences occurs for opposite-sex Twin pairs who shared both prenatal and early postnatal influences and for independent samples of children from different families.
Matthew Strassler - One of the best experts on this subject based on the ideXlab platform.
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The vector-like Twin Higgs
Journal of High Energy Physics, 2016Co-Authors: Nathaniel Craig, Simon Knapen, Pietro Longhi, Matthew StrasslerAbstract:We present a version of the Twin Higgs mechanism with vector-like top partners. In this setup all gauge anomalies automatically cancel, even without Twin leptons. The matter content of the most minimal Twin sector is therefore just two Twin tops and one Twin bottom. The LHC phenomenology, illustrated with two example models, is dominated by Twin glueball decays, possibly in association with Higgs bosons. We further construct an explicit four-dimensional UV completion and discuss a variety of UV completions relevant for both vector-like and Fraternal Twin Higgs models.
Rui Zheng - One of the best experts on this subject based on the ideXlab platform.
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Coscattering/Coannihilation Dark Matter in a Fraternal Twin Higgs Model
Journal of High Energy Physics, 2018Co-Authors: Hsinchia Cheng, Lingfeng Li, Rui ZhengAbstract:Dark matter candidates arise naturally in many models that address the hierarchy problem. In the Fraternal Twin Higgs model which could explain the absence of the new physics signals at the Large Hadron Collider (LHC), there are several viable dark matter candidates. In this paper we study the Twin neutrino in the mass range $\sim$ 0.1--10 GeV as the dark matter. The thermal relic density is determined by the interplay of several annihilation and scattering processes between the Twin neutrino, Twin tau, and Twin photon, depending on the order of the freeze-out temperatures of these processes. Besides the common coannihilation scenario where the relic density is controlled by the Twin tau annihilation, it can realize the recently discovered coscattering phase if the scattering of the Twin neutrino into the Twin tau freezes out earlier than the Twin tau annihilation. We also provide a method to calculate the thermal relic density in the intermediate regime where both coannihilation and coscattering processes contribute to the determination of the dark matter density. We show that the right amount of dark matter can be obtained in various scenarios in different regions of the parameter space. The current experimental constraints and future probes into the parameter space from direct detections, cosmological and astrophysical bounds, dark photon searches, and displaced decays at colliders, are discussed.
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coscattering coannihilation dark matter in a Fraternal Twin higgs model
Journal of High Energy Physics, 2018Co-Authors: Hsinchia Cheng, Lingfeng Li, Rui ZhengAbstract:Dark matter candidates arise naturally in many models that address the hierarchy problem. In the Fraternal Twin Higgs model which could explain the absence of the new physics signals at the Large Hadron Collider (LHC), there are several viable dark matter candidates. In this paper we study the Twin neutrino in the mass range $\sim$ 0.1--10 GeV as the dark matter. The thermal relic density is determined by the interplay of several annihilation and scattering processes between the Twin neutrino, Twin tau, and Twin photon, depending on the order of the freeze-out temperatures of these processes. Besides the common coannihilation scenario where the relic density is controlled by the Twin tau annihilation, it can realize the recently discovered coscattering phase if the scattering of the Twin neutrino into the Twin tau freezes out earlier than the Twin tau annihilation. We also provide a method to calculate the thermal relic density in the intermediate regime where both coannihilation and coscattering processes contribute to the determination of the dark matter density. We show that the right amount of dark matter can be obtained in various scenarios in different regions of the parameter space. The current experimental constraints and future probes into the parameter space from direct detections, cosmological and astrophysical bounds, dark photon searches, and displaced decays at colliders, are discussed.
Walter A Koltun - One of the best experts on this subject based on the ideXlab platform.
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p 182 examination of crohnʼs disease variants in a Fraternal Twin family using exome sequencing and inflammatory bowel disease associated single nucleotide polymorphisms
Inflammatory Bowel Diseases, 2016Co-Authors: Christine S Choi, Joel Coble, Lisa Schneper, Arthur Berg, Leonard R Harris, John P Hegarty, Sue Deiling, James R Broach, Walter A KoltunAbstract:Background:A unique opportunity for genetic investigation was presented by a 3-generation family with Fraternal Twins, one of whom had Crohn's disease (CD) with 2 affected children and the other who was healthy with 3 unaffected children, suggesting an autosomal dominant inheritance. This study test
Margaret Morgan - One of the best experts on this subject based on the ideXlab platform.
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whole genome sequencing for optimized patient management
Science Translational Medicine, 2011Co-Authors: Matthew N Bainbridge, Irene Newsham, J G Reid, Claudia Gonzagajauregui, Wojciech Wiszniewski, David R. Murdock, Jennifer Friedman, Margaret MorganAbstract:Whole-genome sequencing of patient DNA can facilitate diagnosis of a disease, but its potential for guiding treatment has been under-realized. We interrogated the complete genome sequences of a 14-year-old Fraternal Twin pair diagnosed with dopa (3,4-dihydroxyphenylalanine)–responsive dystonia (DRD; Mendelian Inheritance in Man #128230). DRD is a genetically heterogeneous and clinically complex movement disorder that is usually treated with l-dopa, a precursor of the neurotransmitter dopamine. Whole-genome sequencing identified compound heterozygous mutations in the SPR gene encoding sepiapterin reductase. Disruption of SPR causes a decrease in tetrahydrobiopterin, a cofactor required for the hydroxylase enzymes that synthesize the neurotransmitters dopamine and serotonin. Supplementation of l-dopa therapy with 5-hydroxytryptophan, a serotonin precursor, resulted in clinical improvements in both Twins.
